Authentication reader for motor vehicle opening element

ABSTRACT

Disclosed is an authentication reader intended to be installed on a motor vehicle opening element, the reader including a microcontroller, at least one transmitter, at least one matching circuit and a single antenna, called “primary” antenna, characterized by a working frequency. The matching circuit includes switching element able to switch the matching circuit between a first mode, in which the matching circuit makes it possible to match the primary antenna to a secondary antenna of an authentication device whose resonant frequency is lower than the working frequency, and a second mode, in which the matching circuit makes it possible to match the primary antenna to a secondary antenna of an authentication device whose resonant frequency is higher than the working frequency.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/765,445 filed on May 19, 2020, which is the national phase of PCTInternational Application No. PCT/FR2018/052868 filed on Nov. 16, 2018,which claims priority to FR Patent Application No. 1761150 filed on Nov.24, 2017, the contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to the field of unlocking the openingelements of a motor vehicle and relates more particularly to anauthentication reader intended to be installed in an opening element ofa motor vehicle and to an authentication method using such a reader.

Description of the Related Art

Nowadays, it is known to install a near-field communication reader in amotor vehicle opening element, for example on a door handle, in order toallow authentication of a user using a device and unlocking of saidopening element.

Near-field communication (NFC) is based on a short-range andhigh-frequency, for example 13.56 MHz, wireless communication technologyallowing the exchange of information between peripherals up to adistance of a few centimeters, for example of the order of 5 cm.

In practice, when the user of a vehicle wishes to unlock the openingelements thereof, he first of all places his authentication device closeto the reader. The reader then detects the presence of the device, andthen authenticates it and unlocks one or all of the opening elements ofthe vehicle when authentication is successful.

In one known solution, the reader comprises what is called a “primary”antenna and the device comprises what is called a “secondary” antenna.The reader is configured so as to periodically send, via said primaryantenna, an electrical signal in the form of a pulse of short duration,for example a few tens of microseconds. The device may be passive oractive. A passive device may for example be a card or a fob, whereas anactive device may for example be a smartphone or a fob.

When the device comes close enough to the reader, for example within 10cm, the presence of the secondary antenna modifies the voltage acrossthe terminals of the primary antenna. This modification is detected bythe reader, which deduces therefrom that a compatible device is nearby,and then authenticates said device by obtaining and confirming anidentifier stored in a memory area of the device.

FIG. 1 schematically shows one known solution for an authenticationreader 1A. In this solution, the authentication reader 1A comprises amicrocontroller 10A, a transmitter 20A, a matching circuit 30A and aprimary antenna L3. The microcontroller 10A controls the transmitter 20Aso that it excites the primary antenna L3 by way of the matching circuit30A. The matching circuit 30A makes it possible to optimize the transferof the electric power generated by the transmitter 20A between theprimary antenna L3 (source) and the secondary antenna (load, not shown).

To this end, the matching circuit 30A comprises a first branch,connected firstly to the transmitter 20A via a first input terminal E1and secondly to the primary antenna L3 via a first output terminal S1,and a second branch, connected firstly to the transmitter 20A via asecond input terminal E2 and secondly to the primary antenna L3 via asecond output terminal S2. The primary antenna L3 is connected betweenthe first output terminal S1 and the second output terminal S2. Thefirst branch comprises an inductor L1 and a capacitor C1. A capacitor C2is connected in parallel with a resistor R1 between the first outputterminal S1 and ground M. A capacitor C3 is connected between the centertap of the inductor L1 and the capacitor C1 and ground M. The secondbranch comprises an inductor L2 and a capacitor C4. A capacitor C5 isconnected in parallel with a resistor R2 between the second outputterminal S2 and ground M. A capacitor C6 is connected between the centertap of the inductor L2 and the capacitor C4 and ground M. The inductorL1 and the capacitor C3 form a first “LC” filter and the inductor L2 andthe capacitor C6 form a second “LC” filter.

For example:

L1=L2=220 nH

C3=C6=1 nF

C2=C4=128 pF

C2=C5=47 pF

R1=R2=5.1 kΩ

L3=1.7 μH

The nature of authentication devices may however vary significantlydepending on their type (passive fob, active smartphone, etc.) and eachdevice has settings specific to its secondary antenna, in particular itsresonant frequency, its quality factor and its level of coupling withthe primary antenna. The modification of the voltage across theterminals of the primary antenna by the device thus depends on thenature of said device. In particular, some authentication devices willreduce the voltage across the terminals of the primary antenna, whereasothers will increase it, in particular depending on whether theirresonant frequency is lower or higher than the working frequency of theprimary antenna. It then becomes difficult to design a reader such thatit operates with a wide range of authentication devices working atsignificantly different resonant frequencies.

There is therefore a need for a simple and effective reader solutionthat operates with a wide variety of authentication devices.

SUMMARY OF THE INVENTION

The invention relates first of all to an authentication reader intendedto be installed on a motor vehicle opening element, said readercomprising a microcontroller, at least one transmitter, at least onematching circuit and a single antenna, called “primary” antenna,characterized by a working frequency. The reader is noteworthy in thatthe matching circuit comprises switching means able to switch saidmatching circuit between a first mode, in which the matching circuitmakes it possible to match the primary antenna to a secondary antenna ofan authentication device whose resonant frequency is lower than theworking frequency, and a second mode in which the matching circuit makesit possible to match the primary antenna to a secondary antenna of anauthentication device whose resonant frequency is higher than theworking frequency.

The invention thus advantageously allows the reader to match its primaryantenna both to secondary antennas whose resonant frequencies are lowerthan the working frequency and to secondary antennas whose resonantfrequencies are higher than the working frequency, thus making itpossible to authenticate of a wide range of devices.

In a first embodiment, the matching circuit comprises a first branchconnected firstly to the transmitter via a first input terminal andsecondly to the primary antenna via an output terminal and comprising afirst capacitor, the primary antenna also being connected to ground, thematching circuit furthermore comprising a second capacitor connectedfirstly to the output terminal and secondly to ground, and a secondbranch connected firstly to the transmitter via a second input terminaland secondly to the primary antenna at the output terminal andcomprising a first capacitor, the matching circuit furthermorecomprising a second capacitor connected firstly to the output terminaland secondly to ground, and wherein the switching means are in the formof a switching branch connected in parallel with the primary antenna andcomprising a switching capacitor connected in series with a switch.

Preferably, the switch is commanded by the microcontroller or by thetransmitter.

Advantageously, the first branch furthermore comprises an inductor,connected between the first input terminal and the first capacitor, anda third capacitor, connected between the center tap of said inductor andof the first capacitor and ground.

Again advantageously, the second branch furthermore comprises aninductor, connected between the second input terminal and the firstcapacitor, and a third capacitor, connected between the center tap ofsaid inductor and of the first capacitor and ground.

Preferably, the matching circuit furthermore comprises a resistorconnected in parallel with the primary antenna between the outputterminal and ground.

In a second embodiment, the switching means comprise a first switch anda second switch and the matching circuit comprises a branch connectedfirstly to the transmitter via an input terminal and secondly to theprimary antenna via an output terminal, said branch comprising the firstswitch, a first capacitor and the second switch, the first switch beingconnected to the input terminal and being able to switch between a firstconnection point to the first capacitor and a second connection point toground, the matching circuit comprising a second capacitor and a thirdcapacitor, the second switch being connected firstly to the outputterminal and being able to switch between a first connection pointsituated at the center tap between the first capacitor and the secondcapacitor and a second connection point situated at the center tapbetween the second capacitor and the third capacitor, the thirdcapacitor also being connected to ground, the primary antenna beingconnected between the output terminal and ground.

Preferably, the first switch and the second switch are commanded by themicrocontroller or by the transmitter.

Advantageously, the branch furthermore comprises an inductor, connectedbetween the input terminal and the first switch, a fourth capacitor,connected between the first connection point and the second connectionpoint of the first switch, and a fifth capacitor, connected between thesecond connection point of the first switch and ground.

Again advantageously, the reader furthermore comprises a resistorconnected in parallel with the primary antenna, between the outputterminal and ground.

The invention also relates to a motor vehicle comprising at least oneopening element, said opening element comprising an authenticationreader as presented above.

The invention also relates to an authentication system for locking orunlocking at least one opening element of a motor vehicle, said systemcomprising at least one authentication device and a motor vehicle aspresented above.

The invention relates finally to a method for authenticating a device byway of a reader installed in an opening element of a motor vehicle, saidreader comprising a microcontroller, at least one transmitter, at leastone matching circuit and a single antenna, called “primary” antenna,characterized by a working frequency, said method, implemented by saidreader, being characterized in that it alternately comprises the stepsof matching, by way of the matching circuit, the primary antenna to asecondary antenna of a device whose resonant frequency is lower than theworking frequency, and matching, by way of the matching circuit, theprimary antenna to a secondary antenna of a device whose resonantfrequency is higher than the working frequency.

Other features and advantages of the invention will become apparent fromthe following description, provided with reference to the appendedfigures which are given by way of non-limiting example and in whichidentical reference signs are given to similar objects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates one embodiment of a reader from theprior art.

FIG. 2 schematically illustrates one embodiment of the system accordingto the invention.

FIG. 3 schematically illustrates a first embodiment of the readeraccording to the invention.

FIG. 4 schematically illustrates a second embodiment of the readeraccording to the invention.

FIG. 5 schematically illustrates one embodiment of the method accordingto the invention.

FIG. 6 schematically illustrates a first operating mode of the readerfrom FIG. 4.

FIG. 7 schematically illustrates a second operating mode of the readerfrom FIG. 4.

FIG. 8 schematically shows an authentication reader according to theinvention installed in an opening element of a motor vehicle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2 schematically shows a near-field communication authenticationsystem 0 according to the invention.

In this example, the system 0 comprises a first authentication device2-1, for example a passive near-field communication fob, and a secondauthentication device 2-2, for example an active near-fieldcommunication smartphone. The system 0 also comprises an authenticationreader 1B-1, 1B-2 installed in an opening element of a motor vehicle 6as illustrated in FIG. 8, for example in a door 4 or a trunk, inparticular in a door handle.

With reference to FIGS. 3 and 4, the reader 1B-1, 1B-2 comprises amicrocontroller 10B, a transmitter 20B, a matching circuit 30B-1, 30B-2and a single antenna, called “primary” antenna (L4), characterized by aworking frequency, for example 13.56 MHz. It will be noted that themicrocontroller 10B and the transmitter 20B may be separate physicalentities or be implemented by the same physical entity.

The matching circuit 30B-1, 30B-2 comprises switching means able toswitch said matching circuit 30B-1, 30B-2 between a first mode, in whichthe matching circuit 30B-1, 30B-2 makes it possible to match the primaryantenna L4 to a secondary antenna of an authentication device 2-1, 2-2whose resonant frequency is lower than the working frequency, and asecond mode, in which the matching circuit 30B-1, 30B-2 makes itpossible to match the primary antenna L4 to a secondary antenna of anauthentication device 2-1, 2-2 whose resonant frequency is higher thanthe working frequency.

FIGS. 3 and 4 schematically show two embodiments of the authenticationreader 1B-1, 1B-2 according to the invention.

First of all, in the first embodiment illustrated in FIG. 3, thematching circuit 30B-1 comprises a first branch B1 and a second branchB2. The first branch B1 is connected firstly to the transmitter 20B viaa first input terminal E11 and secondly to the primary antenna L4 via anoutput terminal S11. The second branch B2 is connected firstly to thetransmitter 20B via a second input terminal E21 and secondly to theprimary antenna L4 at the output terminal S11. The primary antenna L4 isconnected between the output terminal S11 and ground M.

The first branch B1 first of all comprises an inductor L5 connectedfirstly to the first input terminal E11 and secondly to a firstcapacitor C7, the first capacitor C7 also being connected to the outputterminal S11. A second capacitor C8 is connected between the outputterminal S11 and ground M. A third capacitor C9 is connected between thecenter tap of the inductor L5 and the first capacitor C7 and ground M.The inductor L5 and the third capacitor C9 (which are optional)advantageously form an LC filter making it possible to rejectlow-frequency and high-frequency signals.

The second branch B2 first of all comprises an inductor L6 connectedfirstly to the second input terminal E21 and secondly to a firstcapacitor C10, the first capacitor C10 also being connected to theoutput terminal S11. A second capacitor C11 is connected between theoutput terminal S11 and ground M. A third capacitor C12 is connectedbetween the center tap of the inductor L6 and the first capacitor C10and ground M. The inductor L6 and the third capacitor C12 (which areoptional) advantageously form an LC filter making it possible to rejectlow-frequency and high-frequency signals.

In this example, the matching circuit 30B-1 furthermore comprises aresistor R3 connected between the output terminal S11 and ground M, thatis to say connected in parallel with the primary antenna L4. Thisresistor R3 makes it possible to adjust the quality factor of theprimary antenna L4.

In this first embodiment, the switching means are in the form of aswitching branch connected in parallel with the primary antenna L4 (andtherefore also with the resistor R3) and comprising a switchingcapacitor C13 connected in series with a two-position switch M1

(open or closed). In this example, the switch M1 is a MOSFET transistor,but any other suitable type of switch could be used. One of themicrocontroller 10B or the transmitter 20B is configured so as tocommand the switch M1 periodically, for example every 200 ms.

The values of the components of the matching circuit 30B-1, inparticular of the capacitors C7, C8, C10 and C11, are chosen such thatthe primary antenna L4 is matched to a secondary antenna whose resonantfrequency is lower than the working frequency when the switch M1 is inone position, and matched to a secondary antenna whose resonantfrequency is higher than the working frequency of the primary antenna L4when the switch M1 is in its other position (for example the switch M1is closed when the input terminal E11 is active).

For example:

L4=1 pH

L5=220 nH

L6=1.5 pH

C7=36 pF

C8=9 pF

C9=100 pF

C10=22 pF

C11=76 pF

C12=100 pF

C13=12 pF

R3=2 kΩ

In the second embodiment illustrated in FIG. 4, the switching meanscomprise a first two-position switch I1 and a second two-position switchI2, for example of MOSFET transistor type.

The first switch I1 is able to switch between a first connection pointP1 and a second connection point P2.

Similarly, the second switch I2 is able to switch between a firstconnection point P3 and a second connection point P4.

One of the microcontroller 10B or the transmitter 20B is configured soas to command the first switch I1 and the second switch I2simultaneously and periodically, for example every 200 ms.

The matching circuit 30B-2 is connected firstly to the transmitter 20Bat an input terminal E12 and secondly to the primary antenna L4 at anoutput terminal S12.

The matching circuit 30B-2 first of all comprises an inductor L7connected firstly to the input terminal E12 and secondly to the firstswitch I1.

The first connection point P1 of the first switch I1 is connected to afirst capacitor C16, which is also connected to the first connectionpoint P3 of the second switch I2.

The matching circuit 30B-2 comprises a second capacitor C17 and a thirdcapacitor C18. The second capacitor C17 is connected firstly to thefirst capacitor C16, at the first connection point P3 of the secondswitch I2, and secondly to the third capacitor C18, at the secondconnection point P4 of the second switch I2, the third capacitor C18also being connected to ground M.

The matching circuit 30B-2 furthermore comprises a fourth capacitor C19,connected between the first connection point P1 and the secondconnection point P2 of the first switch I1, and a fifth capacitor C20,connected between the second connection point P2 of the first switch I1and ground M.

The inductor L7, the fourth capacitor C19 and the fifth capacitor C20(which are optional) advantageously form an LC filter making it possibleto reject low-frequency and high-frequency signals.

In this example, the matching circuit 30B-2 furthermore comprises aresistor R4 connected between the output terminal S12 and ground M, thatis to say connected in parallel with the primary antenna L4. Thisresistor R4 makes it possible to reject low-frequency and high-frequencysignals.

The values of the components of the matching circuit 30B-2, inparticular of the capacitors C16, C17 and C18, are chosen such that theprimary antenna L4 is matched to a secondary antenna whose resonantfrequency is lower than the working frequency when the first switch I1and the second switch I2 are in a first configuration, and matched to asecondary antenna whose resonant frequency is higher than the workingfrequency of the primary antenna L4 when the first switch I1 and thesecond switch I2 are in a second configuration, as will be describedbelow.

For example:

The capacitors C19 in series with C20 have an equivalent capacitance of180 pF

The capacitors C16 in series with C17 have an equivalent capacitance of74 pF

C18=258 pF

C20=1 nF

The capacitors C19 in series with C16 have an equivalent capacitance of234 pF

The capacitors C17 in series with C18 have an equivalent capacitance of153 pF

R4=3.3 KΩ

L4=0.78 pH

L7=220 nH

The invention will now be described in terms of the implementationthereof with reference to FIGS. 5 to 7.

With reference first of all to FIG. 5, the implementation of theinvention consists in the microcontroller 10B commanding the transmitter20B such that it generates at least one electric current in the matchingcircuit 30B-1, 30B-2 allowing the primary antenna L4 to alternately senda first electrical signal to the secondary antenna of an authenticationdevice 2-1, 2-2 in a step E1 during which the matching circuit 30B-1,30B-2 operates in a first mode, and a second electrical signal to thesecondary antenna of an authentication device 2-1, 2-2 in a step E2during which the matching circuit 30B-1, 30B-2 operates in a secondmode, the first mode and the second mode being defined by the positionof the switching means.

In a first mode of implementation relating to the first embodiment ofthe reader 1B-1 (cf. FIG. 3), the microcontroller 10B or the transmitter20B commands the switch M1 so that it is alternately open or closed,such that the matching circuit 30B-1 makes it possible to alternatelymatch the primary antenna L4 to two types of secondary antennas, asexplained above.

In a second mode of implementation relating to the second embodiment ofthe reader 1B-2 (cf. FIG. 4), the microcontroller 10B or the transmitter20B commands the first switch I1 and the second switch I2 simultaneouslyand periodically such that the matching circuit 30B-2 operatesalternately in a first mode or in a second mode.

With reference to FIG. 6, which illustrates the operation of the circuitof the second embodiment of the reader 1B-2, the first mode is definedby the position of the first switch I1 in which the inductor L7 isconnected to the first capacitor C16 and by the position of the secondswitch I2 in which the center tap P1 of the second capacitor C17 and ofthe third capacitor C18 (i.e. corresponding to the second connectionpoint P4 of the second switch I2) is connected to the output terminalS12.

In this case, as illustrated in FIG. 6, the matching circuit 30B-2comprises:

-   -   the LC filter consisting of the inductor L7 and a branch where        the fourth capacitor C19 and the fifth capacitor C20 are in        series and connected to ground M,    -   the first capacitor C16 and the second capacitor C17 connected        in series firstly to the inductor L7 (via the first switch I1        and the point P1) and secondly to the output terminal S12 (via        the second switch I2 and the point P4),    -   the third capacitor C18, the resistor R4 and the primary antenna        L4, all three of them connected in parallel between the output        terminal S12 and ground M.

With reference to FIG. 7, the second mode is defined by the position ofthe first switch I1 in which the inductor L7 is connected to the centertap P2 between the fourth capacitor C19 and the fifth capacitor C20 andby the position of the second switch I2 in which the center tap of thefirst capacitor C16 and of the second capacitor C17 (i.e. correspondingto the second connection point P3 of the second switch I2) is connectedto the output terminal S12.

In this case, as illustrated in FIG. 7, the matching circuit 30B-2comprises:

-   -   the LC filter consisting of the inductor L7 and the fifth        capacitor C20,    -   the fourth capacitor C19 and the first capacitor C16 connected        in series firstly to the inductor L7 (via the first switch I1        and the point P2) and secondly to the output terminal S12 (via        the second switch I2 and the point P3),    -   a branch (comprising the second capacitor C17 and the third        capacitor C18 connected in series), the resistor R4 and the        primary antenna L4, all three of them connected in parallel        between the output terminal S12 and ground M.

Alternately using the two modes advantageously makes it possible tomatch the primary antenna L4 alternately to a secondary device antenna2-1, 2-2 operating at a resonant frequency lower than the workingfrequency of the primary antenna L4 and to a secondary device antenna2-1, 2-2 operating at a resonant frequency higher than the workingfrequency of the primary antenna L4. The switching frequency between thefirst mode and the second mode is chosen so as to allow rapid detectionof one or the other type of device 2-1,

2-2 (switching may for example be performed several times per second).

The invention claimed is:
 1. An authentication reader for a motorvehicle opening element, said authentication reader comprising: amicrocontroller; at least one transmitter; a single primary antennahaving a working frequency; and at least one matching circuit comprisinga switch system configured to switch said at least one matching circuitbetween a first mode in which the at least one matching circuit permitsthe primary antenna to match a secondary antenna of an authenticationdevice having a resonant frequency lower than the working frequency, anda second mode in which the at least one matching circuit permits theprimary antenna to match a secondary antenna of another authenticationdevice having a resonant frequency higher than the working frequency,the switch system comprising a first switch and a second switch, abranch connected to: (i) the at least one transmitter via an inputterminal, and (ii) the at least one primary antenna via an outputterminal, said branch comprising the first switch, a first capacitor,and the second switch, the first switch being connected to the inputterminal and being configured to switch between a first connection pointfor connection to the first capacitor and a second connection point forconnection to the ground, a second capacitor, and a third capacitorconnected to the ground, wherein the second switch is connected to theoutput terminal and is configured to switch between a first connectionpoint situated at the center tap between the first capacitor and thesecond capacitor, and a second connection point situated at the centertap between the second capacitor and the third capacitor, and the singleprimary antenna is connected between the output terminal and the ground.2. The authentication reader according to claim 1, wherein the branchcomprises an inductor connected between the input terminal and the firstswitch, a fourth capacitor connected between the first connection pointand the second connection point of the first switch, and a fifthcapacitor connected between the second connection point of the firstswitch and the ground.
 3. A motor vehicle, comprising: at least oneopening element, said at least one opening element comprising theauthentication reader as claimed in claim
 1. 4. A motor vehicle,comprising: at least one opening element, said at least one openingelement comprising the authentication reader as claimed in claim
 2. 5.An authentication system for locking or unlocking the at least oneopening element of the motor vehicle as claimed in claim 3, saidauthentication system comprising: at least one authentication device;and the motor vehicle.
 6. An authentication system for locking orunlocking the at least one opening element of the motor vehicle asclaimed in claim 4, said authentication system comprising: at least oneauthentication device; and the motor vehicle.